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K1 / K2 spring kit

A few weeks ago i changed oil and filter of an automatic transmission from a friends W126. He had troubles with hard shift and slipping gear. For that reason we also replaced the K1 and K2 springs. He ordered the parts as i have no experiance with this K1 and K2 spring kits!
It turned out to be a major improvement for the transmission. It shifts very smooth now, almost perfect.

When i am going to change oil and filter for the E500 and 400E i want to replace the springs also and hope to get an improvement in shift too. Also as a "while i am in there" thing.

What i know about the spring kit is:

The K1 spring kit (new type) is universal and has partnumber A126 270 4477
That should fit in our transmissions?

The K2 spring kit has multiple partnumbers: A126 270 xx35
Witch one should i order for our transmissions?

I searched the forum for this subject but could not find anything pointing to this partnumbers?

The costs of the kit's ordered at the dealer are under $10 each, so that is why i think it is worth it to replace them?

Re: K1 / K2 spring kit

There have been some changes to the springs through the years. Some of those springs were in a TSB on our ng, some are for 722.4xx, and some address specific issues. The K2 is the example there.

There is a superior shift kit available for ~ $45. It has several options for making the shifts firmer or softer.

Those kits are the accumulator kits. I went through last year and ordered every one available and experimented. No notes in my hand- but I believe for most(unless you have a broken spring), that you can replace the K2(effecting 2-->3 shift) and move the old K2 into the K1 position. Monkeying with the shift kit plan on removing and changing springs 2 or 3 times. K1 and K2 are on either ends of the same spool. So changing one effects the other...

You can turn up the pressure slightly which will quicken shifting. Clean fluid will improve shifting.

Is it worth replacing them? If you are not experiencing a problem- don't touch it. If you want to improve something- please give us more details on how it is shifting.

I've got a 1992 first gear start valve body built with improvements, just hasn't been tested yet.

K1 / K2 spring kit

Is it worth replacing them? If you are not experiencing a problem- don't touch it. If you want to improve something- please give us more details on how it is shifting.

Michael

Thanks Michael,

I have 3 cars with automatic transmission. All of them shift ok, but can be improved because the shifts 2-3 3-4 can be "firm". Not really something to worry about but when this can be fixed with new K1 and K2 springs, why not do that? It dont costs much.
I read about the superior kit but thought of keeping the partnumbers original Mercedes.
After replacing them in the W126 the other day i was surprised of the effect. Better than only an oil and filter change.
Is it not so that the springs wear out a little after so many years and replacement is a good thing?
My thought was to change the springs as a job while i am in there. There must be a valid K2 mercedes partnumber for 400/500 transmissions?
Changing the springs only still is a time consuming job so i prefer not to experiment with that. When i am not sure about the right parts i will leave it alone.

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Re: K1 / K2 spring kit

The K1 factory spring upgrade (126-270-44-77) will slightly firm up the 2-3 upshift. You only want to do this if the 1-2 and 3-4 shifts are normal, but 2-3 is soft or flaring. Also, it's possible a previous owner may have already installed this, can't tell until you remove the old one and measure the wire diameter on the springs (they are 0.1-0.2mm thicker on the new springs). I'm not aware of any factory spring upgrade for the K2, which affects the 3-4 upshift.

The Superior kit allows going even firmer beyond what the 126-270-44-77 will do, along with parts to adjust other shifts. Again, unless you are having shift issues, I wouldn't mess with anything. Pics of the Superior kit, and their instruction sheet, are here:http://124performance.com/images/W12...erior_springs/

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K1 / K2 spring kit

After contact with the owner of the W126, these are the 2 mercedes partnumbers we build in the transmission. I will order the 2 and decide when i change fluid and filter If i replace the spring kit's. I think he payed only 12-14 dollar for the 2 kits.
Thanks for all the input so far!

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Re: K1 / K2 spring kit

Hakie,

Maybe you need to lower the line pressure slightly if all your shifts are too firm? As a rule, springs don't settle if made properly. Manytimes, you will find a broken spring where a rust pit had started and it failed with fatigue cycling. You can read the superior's information, but I know it has several springs for each K1 and K2. I think you can go softer, firm or extra firm. MB kits are nice between the color coordination and you get new seals.

Re: K1 / K2 spring kit

Maybe you need to lower the line pressure slightly if all your shifts are too firm? As a rule, springs don't settle if made properly. Manytimes, you will find a broken spring where a rust pit...

Yes Michael, i think the best thing to do is inspect the springs first and than decide what to do. It is not a big problem in my case. Also it is a bit complicated for me to explain the situation. I find therms as "hard, harsh and firm" shifts.
Maybe i just have to live with it. The cars are all 20+ years old and that comes with some wear in the trans.
Also the oil and filter change can change the feel of shifting. The cars are in winter season soon. In that period i will do de transmission maintenance.

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Re: K1 / K2 spring kit

The type of ATF can change shift quality... in general, fully-synthetic can provide slightly more consistent shifts between cold and hot. If you change from a Dexron-III spec (7.5 viscosity) to a Dexron-VI spec (6.0 viscosity) you may need to adjust the vac modulator, and/or possibly fiddle with some springs. I prefer to use the fluid spec the 722.3/4/5/6 was originally designed for (7.5 cSt) but that's just me. There's been discussion / debate about this in other forum threads.

Also, if ALL the shifts are too firm or too soft, this can be adjusted via the vacuum modulator. If the vacuum modulator is original or old, it is not a bad idea to replace it, I had some intermittent odd shifting (flaring, IIRC) on one transmission which was cured with a new modulator.

Re: K1 / K2 spring kit

Originally Posted by gsxr

The K1 factory spring upgrade (126-270-44-77) will slightly firm up the 2-3 upshift. You only want to do this if the 1-2 and 3-4 shifts are normal, but 2-3 is soft or flaring.

Very important note! Please do consider this.
Normally its used because 2-3 upshift ist the most used shift on these boxes and it wears out at first (besides the reverse). So its starts to get super soft (and long) and then flares.
On my gearbox i did this spring update preemptively without knowing the gearbox, nor driven it. The result is that all shifts are good, but the 2-3 is veeeery quick and clearly noticable. I played around alot with the modulating pressue which adjusts shift speed and softness for all gearshifts, but when i do the pressur so that 2-3 shift is perfect, all other shifts are tooo soft and take to long (almost flare).

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Re: K1 / K2 spring kit

Originally Posted by Christian_K

On my gearbox i did this spring update preemptively without knowing the gearbox, nor driven it. The result is that all shifts are good, but the 2-3 is veeeery quick and clearly noticable. I played around alot with the modulating pressue which adjusts shift speed and softness for all gearshifts, but when i do the pressur so that 2-3 shift is perfect, all other shifts are tooo soft and take to long (almost flare).

So you mean, if I want to swap a transmission, I shouldn't do it? As it's what I'm just intended to do.
Never driven the trans, should be just fine. 600SEC though. And my car isn't stock either. (510hp)
Okay, maybe, I'll get a fluid flush and we'll see how it goes. Also I really want the 1st gear start badly.

Anyway, I stongly recommend anyone to use Dexron-II in the gearbox. DxIII is way weaker and burns clutches. DxII makes shifts quick and stable, although feels strange when cold.
I'm looking forward pouring Redline Type-F ATF with 10cct viscosity index.

What brand are you purchasing D2 fluid? I don't understand what you mean when you say a fluid is "weaker and burns clutches". Is the viscosity lower?

I'm running redline in mine now- shifts are fine. Quick and crisp with the v/b changes. But it was a lot of work. For most, I bet they can do a shift kit/new flluid and then play with modulator pressure a bit and be happy- if the transmission is healthy. Type F fluid has [no] friction modifiers and seems to help if you have glazed some discs. It may help, but you should start saving coins for a rebuild.

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Re: K1 / K2 spring kit

Yeah, I know that Type-F has no friction modifiers, which is good. A friction modifiers decrease friction. With few cars on Dexron-III or universal ATF (Castrol universal ATF, Chevron D/M, as recommended by some 722.9 trans guru), I've experienced weak clamping force, overall smooth behaviour of 722.3, which is not what it's intended to do. I managed to flush the system with simple Mobil 220 and became brilliant. No clunking or whatever at idle, but great clamping force and strong shifts. Which is what I like when my right foot is heavy.
Now I thought, maybe I was wrong, allowed a Chevron D/M fluid flush with a v/b interchanged on my other 722.3. And it cooked up within half a year. It was really better on Dx2. So... no.. I think I'll never use anything other than Dx2 in 722.3. I wanted to try synthetic Dx2, but found out that it's lower viscosity. So only option is get a big trans radiator if you want a stable Dx2 operation. Or maybe try Type-F as well. Redline's Type-F is 10cct. So it's a little like mid-cold Dexron-2.

I wonder what happens with high modulator pressure on type-F? is it faster?
My intention is to make the trans shift faster with higher pressure. But logic tells that due to higher viscosity the actual shift time may not be fast.

Also on a new old stock E500 trans under heavy acceleration I've had 2-3 flare. Tried to correct it with higher pressure, went better, until the fluid heats up too much and a slight flare appears. The fluid was Dx2 though. That's probably when you should get ...4477 2-3 flare kit.

Re: K1 / K2 spring kit

Understand now Alex- sorry I was a little slow or harsh.

I think modulator pressure shortens the shift time. It fills the accumulator thicker- now cold. With cold weather running you might experience- I would do Redline race which is a thicker type-F. I've experienced recently a 2-3 flare and it was corrected by checking the fluid level which was ~ 0.5 liter low.
I think the synthetic versions are better as the viscosity range is narrower over operating range. My aux trans cooler fan seems to run most when idling at a stop. I think someone mentioned racing and only seeing transmission temp of 200F on the track.

Re: K1 / K2 spring kit

Originally Posted by whatever

Yeah, I know that Type-F has no friction modifiers, which is good. A friction modifiers decrease friction. With few cars on Dexron-III or universal ATF (Castrol universal ATF, Chevron D/M, as recommended by some 722.9 trans guru), I've experienced weak clamping force, overall smooth behaviour of 722.3, which is not what it's intended to do. I managed to flush the system with simple Mobil 220 and became brilliant. No clunking or whatever at idle, but great clamping force and strong shifts. Which is what I like when my right foot is heavy.
Now I thought, maybe I was wrong, allowed a Chevron D/M fluid flush with a v/b interchanged on my other 722.3. And it cooked up within half a year. It was really better on Dx2. So... no.. I think I'll never use anything other than Dx2 in 722.3. I wanted to try synthetic Dx2, but found out that it's lower viscosity. So only option is get a big trans radiator if you want a stable Dx2 operation. Or maybe try Type-F as well. Redline's Type-F is 10cct. So it's a little like mid-cold Dexron-2.

I wonder what happens with high modulator pressure on type-F? is it faster?
My intention is to make the trans shift faster with higher pressure. But logic tells that due to higher viscosity the actual shift time may not be fast.

Also on a new old stock E500 trans under heavy acceleration I've had 2-3 flare. Tried to correct it with higher pressure, went better, until the fluid heats up too much and a slight flare appears. The fluid was Dx2 though. That's probably when you should get ...4477 2-3 flare kit.

Good questions..

On the type F I find I can Typically dial back modulator pressure some and still keep Quick/Positive shifts. One of the Many reasons I'm such a fan of F...be it conventional or synthetic (redline racing atf is the most reliable source these days).

What/where are you running your car hard enough to really get the trans HOT...? We do endurance racing w/ the track rat so she gets 2.5 hour stints 8-10 hours @ a clip. Right now we're running a large hayward And the trans cooler from a W140 S600 Euro..even comes with a nice little fan that we have switched for when we come into the pits.

I think you would Really like the Redline fluid. I sure do!

If you REALLY want a bangin' valve body rock out that Superior kit. the directions kinda suck and you might have to improvise a little for the 1-2 shift but it does a damn good job.

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K1 / K2 spring kit

Last week i did the oil and filter change on the 400E. Also while i was there, changed the K1 and K2 spring kits. I am not sure what cured what but the transmission shifts as i would like it. Sometimes cant even notice up-shifting.
I think the new filter and oil also did good, maybe all. I would not be surprised if it was the first time the whole transmission was drained.
First time job on the 400E. (Not a car mechanic) I left the cross-over exhaust in place. That was kinda pita and i will never do that again. Sure was a good "exercise" for the job to my E500. Will do that coming winter.
I used oil and filter from the dealer.
Only thing i have noticed is while downshifting manually from 4-3 the shift is hard. Any idea's to solve this or is this not to worry about?IMG_3512.JPGIMG_3514.JPG